Lighting/signaling systems are important navigational aids for aircrafts, boats, or other vehicles, in providing guidance, signaling, and demarcation functions therefore. Semiconductor light emitting devices, preferably light emitting diodes (LEDs), have been identified to be the replacement for the conventional incandescent or electrical discharge lamps that are employed in the current navigational lighting/signaling systems. LEDs offer many advantages over incandescent or electrical discharge lamps. These advantages include but are not limited to high energy efficiency, long lifespan, low maintenance cost, enhanced reliability and durability, as well as no lumen loss induced by filtering.
Visible navigational LEDs are ‘cold’ light sources that produce less heat or infrared emission than the conventional incandescent lights. However, in certain cases, the infrared emission produced by the incandescent navigational lights is useful. For example, search/rescue teams may use the heat signature of an incandescent lamp in a conventional buoy lantern to locate the stranded crew with their night vision equipments such as night vision goggles (NVGs) or forward looking infrared (FLIR) equipments. When boaters are stranded, they will radio their location referencing particular buoys as the coordinates and the search/rescue team will fly to a location according to those coordinates. During the operation, NVGs or FLIRs are used to search for thermal signatures of boaters under water and in the mean time to see the buoy coordinates which have the infrared emission. As another example, lighting/signaling apparatus with infrared emission may be used for navigation during covert operations.
Infrared LEDs are known to be used as signal beacons and airport runway lighting apparatus.
U.S. Pat. No. 5,804,829 to Palmer describes a portable signal beacon adapted to be worn on the body so as to provide a discernable signal to a remote observer. The signal beacon includes a lightweight housing containing a bank of infrared LEDs. A signal generating device controls the activation of the LED light source and provides the LED light source with one of a plurality of different flashing sequences. The portable design of the disclosed signal beacon is not suitable for permanent or semi-permanent navigational applications where a much higher light intensity is required.
U.S. Pat. No. 7,023,361 to Wallace et al. describes a runway lighting fixture of the type normally permanently installed at an aircraft installation such as an airport to provide visible light signals to an aircraft, the fixture having an internal, non-visible light source such as an infrared lamp capable of being activated to provide a non-visible light signal to an aircraft specially equipped to see such non-visible signals. The lighting fixture comprises a standard incandescent or quartz lamp as the visible light source and an array of infrared LEDs as the non-visible light source. The visible and the non-visible light sources are independently powered and emit from separate light-emitting windows. Due to the fact that the disclosed the lighting fixture still comprises lamp based light sources, it suffers similar disadvantage as conventional lamp based navigational lights.
Neither of the Palmer and Wallace patents discloses an intention to control the beam profile of the LEDs to produce a well defined spatial distribution of light intensity, which is required by many national or international standards, such as FAA, NOAA, ICAO, UK-CAA, and/or NATO standards for navigational lights.
There thus exists a need for an all solid state lighting/signaling apparatus for permanent or semi-permanent navigational applications. The lighting/signaling apparatus produces visible as well as infrared emission with well defined beam profile and intensity distribution for navigation and search/rescue applications employing night vision equipments.